Frequently Asked Questions

1.1 How can I participate?

Please create an account at the login screen (see the figure below) and then login to participate in the GALAXY CRUISE galaxy classification. We require accounts to allow us to manage everyone's classification results. For more information about the registration process, please see “2. About Account Registration.”
* You can access pre-login content without registering.

Season 2 login screen


1.2 What do I need to participate?

To participate in this project, you need a PC or tablet connected to the internet. GALAXY CRUISE’s website is optimized for PC and tablet browsers. Please perform the classification with your device connected to the internet so that you can load image data and save your classification results. A reasonable internet speed (16 Mbps or higher) is recommended.
Test your internet speed

1.3 Can I participate from my smartphone?

We recommend using a PC or tablet to participate in this project; however, a smartphone with a smaller screen can also be used for galaxy classification.

1.4 Can I view the images of galaxies without registration?

The same images that are used in GALAXY CRUISE can be accessed through the hscMap viewer, which allows you to browse the images captured during the HSC Subaru Strategic Program (HSC-SSP). It is publicly accessible and does not require registration. However if you want to participate in the galaxy classification, you need to register with GALAXY CRUISE.
 Exploring the Universe with Subaru Telescope Data  (About hscMap)
 Unique Galaxies Hiding in the Cosmic Images  (June 1, 2020, GALAXY CRUISE NEWS)


2.1 Where can I create my account?

You can create your account from the login screen. First click the “CREATE ACCOUNT” button, then enter your e-mail address and create a password. Then click the “Register” button. You should then receive an automatic e-mail with a link. Please click on the link in the e-mail to display the registration screen for your account name and other informationA simple questionnaire will be displayed upon registration, so please fill it out. Please complete the required information and click the “Register” button to complete the registration process. Registration is of course free. 
* Those who have already signed up for Season 1 can log in to Deep Quest with the same account.
* Your account name is your virtual identity that will be displayed on the rankings screen after login.
* These questionnaire items will be used for future programs. Attributes and motivation are analyzed as statistically, separately from personal information, and individuals will not be identified.

2.2 Why didn’t I receive the automatic e-mail?

Please check your e-mail settings. The possible causes are:
・The e-mail was automatically sorted into your spam folder.
The e-mail might have been delivered to your spam folder instead of your inbox.
・Spam protection is active.
If your cellphone is set to only receive e-mails from specific domains in order to avoid spam, it might have blocked the automatic e-mail. Please modify your e-mail settings to allow messages from the following three domains:,, and
・An incorrect e-mail address was registered.
Please double check that the e-mail address entered into the registration form is correct. If the e-mail address you provided us with is not correct, we will be unable to send you the confirmation e-mail.
*If you try these three solutions and the problem still persists, please contact us.

2.3 Why can’t I log in?

To log in, you need your registered login ID (your e-mail address) and password. (If you haven’t yet registered, please create your account first.) Please verify that all the required information is entered correctly and then try to log in again. Note that all information must be entered in single-byte characters. 
* If you have verified the registration information but still cannot log in, please contact us.

2.4 What should I do if I forget my login password?

Click “Reset Password” on the login screen and create a new password.
* If you have trouble logging in when using a different browser than normal, please reset your password. 

2.5 How can I modify my registration information?

After login, click the suitcase-shaped icon at the bottom left of the screen and open the “Voyage Log” (see the figure below). If you click the “Change Registration Information” button, another screen will pop up where you can change your account name and password.



2.6 How can I display my avatar on the Ranking screen?

First, click the “Change Registration Information” (see “2.5” above for more information about the "Change Registration Information" button) and open “Registration Information” (see the figure below). To display your avatar, select the “Use Gravatar” and “Show my Gravatar on Rankings” boxes on the bottom left of the page. When selected, a checkmark (✓) should appear in the box. Finally click the “Save” button on the bottom right to save your changes. 
* If you remove the checkmark from the “Show my Gravatar on Rankings” box, your avatar will appear only on the “Registration Information” screen.
* Creating a  Gravatar (Globally Recognized Avatar) is the only way to upload your avatar image to this website.


2.7 How can I create a Gravatar?

To To create a Gravatar, you need an account on If you don’t have one, visit the official website of “Gravatar” and click the “Create Your Own Gravatar” button to sign up. Upon signing up, please make sure to use the same e-mail address you used to register for GALAXY CRUISE. (If you have a account, click the “Sign In” button to access your account.) Once you have created your avatar at the “My Gravatars/Manage Gravatars” page after login, you can view your avatar image on the “Voyage Log.” (Provided you have selected the “Use Gravatar” box on the “Registration Information” screen explained in “2.6” above.)

2.8 Can I delete my account?

Yes. To delete your account, open “Voyage Log” (as explained in “2.5” above) and click the “Delete Account” button to delete your registration information (such as e-mail address) and the number of galaxies you have classified. However, your classification results are stored separately from your account-related information, and will be used in future research. Note that you cannot delete your classification results.

3.1 Can I log in to Deep Quest with the same account as Season 1?

Yes. Please log in from the login screen of Deep Quest by entering the account name (email address) and password registered in Season 1.

3.2 Can I still log in to Season 1?

Yes. Even after the departure of Deep Quest, you can still log in to the Season 1 classification screen to view your Voyage Log and collected departure stamps and souvenirs. However, the galaxy classification function on this screen will be removed at 11:59 p.m. on April 25, 2022 (JST). To continue galaxy classification, please log in to Deep Quest. Although you can continue exploring cosmic images captured by the Subaru Telescope in Season 1, Deep Quest has the same feature, and you are thus encouraged to migrate to Deep Quest.

3.3 Can I move directly from Deep Quest to the Season 1 classification screen?

No. To do so, you need to log out from Deep Quest and then log in again from the login screen of Season 1. To reach the Season 1 login screen, please click “Click here if you want to log in to Season 1” below the login screen of Deep Quest.

3.4 Are the images used in Deep Quest different from those in Season 1? 

The images used in both seasons are from the second public data release of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP), which has surveyed deep into extensive regions of the sky for 330 nights with Hyper Suprime-Cam (HSC) on the Subaru Telescope. These data (images) were published in May 2019. Galaxies to be classified in Deep Quest are within the same distance range* as in Season 1, but fainter than those in the previous season. Your classifications of fainter galaxies will make even more detailed scientific analysis possible. The reason why the same dataset is used is to analyze blighter and fainter galaxies in the same way.
* Galaxies about 2.4 billion years ago or later (at redshifts 0.2 or lower)


3.5 How are the towns and continents in Season 1 related to the islands and archipelagos in Deep Quest?

Please see the table comparing the two seasons under “About the Cruise Map.”
The towns and continents in Season 1 correspond respectively to the major islands and archipelagos in Deep Quest. Some archipelagos are further divided into several islands. In Season 1, you may have toured around multiple continents, but in Deep Quest you will cruise around an ocean dotted with many islands.


3.6 Is there any difference between Season 1 and Deep Quest in the ways the voyages progress?

Yes. In Season 1, you traveled in order from Stage 1 to Stage 10. However in Deep Quest, your next destination will change depending on your progress on the voyage: once you complete an island or an archipelago, you should move on to the “active” island, the place where classification is being conducted most actively. By classifying galaxies there in cooperation with other Citizen Astronomers, you will unlock access to a new island or archipelago.
About the Deep Quest Mission


4.1 About the world view

Our Milky Way Galaxy is a shimmering isle of light in the black sea of intergalactic space. But we are not alone; innumerable galaxies lie scattered across the void like an archipelago full of diversity. GALAXY CRUISE is your chance to explore this cosmic archipelago. HSC mounted on the Subaru Telescope, one of the world’s best astronomy telescopes, has imaged countless galaxies scattered across a depth of billions of light-years of space. Likening the whole region of the sky surveyed by the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) to a nautical chart (the cruise map), with each galaxy you will come across wonderful scenery, as if you were on a cruise ship sailing on a world tour.
Deep Quest (Season 2) Cruise Map
Season 1 Cruise Map

4.2 What can I earn by participating in the galaxy classification?

In Deep Quest, you will earn a piece of a puzzle as a “souvenir” every time you classify 100 galaxies. You will also receive a departure stamp when you complete each major island or archipelago. Collected souvenirs and stamps can be viewed on the welcome screen after login.
About Rewards (Deep Quest)
About Rewards (Season 1)

4.3 Completion of the cruise

When you complete all the islands and archipelagos and earn the departure stamp at the last archipelago, you will have completed the journey of GALAXY CRUISE Deep Quest. Thank you for your generous support of astronomy research to unlock the mysteries of galaxy evolution. You can end your journey partway through if intervening circumstances arise. For more details, see “2.8 Can I delete my account?” 

5.1 I have no idea which galaxies to classify.

White crosshairs will appear on a galaxy to be classified and if you zoom in on the galaxy, the crosshairs will disappear. If you lose track of which galaxy you are looking at, zoom out to display the crosshairs again. (You can zoom in and out by using your mouse wheel or touchpad.)
Classification Procedure

5.2 What should I do when white crosshairs or a green checkmark (✓) obscures the galaxies?

Using your mouse wheel or touchpad, you can zoom in to clear the white crosshairs on an unclassified galaxy or the green checkmark (✓) on a classified galaxy. Please magnify the images of galaxies so that you can inspect their detailed structures before classifying them.
* In Deep Quest, the crosshairs and the checkmark can be turned on and off at your discretion.

5.3 I see a bright galaxy off-centered of the white crosshairs.

When you encounter such a galaxy, please classify the brightest galaxy close to the center of the white crosshairs. This problem seems to happen for some bright galaxies, not faint ones.

galaxy off-center of the white crosschairs


5.4 In what situations should I adjust the brightness or convert to grayscale?

Faint structures, the features of galaxy interactions, may be lurking around the main body of galaxies. Sometimes it is easier to discover these faint structures by adjusting the brightness or converting to grayscale.

5.5 I understand the first question for classification has only three options: “Spiral Galaxy” “Elliptical Galaxy” and “Neither.” Which options should I select when I identify a galaxy as a “lenticular” or an “irregular”?

You should select “Spiral Galaxy” only when you find a spiral structure in that galaxy. However, please note that, as explained in Lesson 1 (Introductory), some spiral galaxies may appear edge-on. Lenticulars (also called S0 galaxies) are intermediate between spirals and ellipticals and have no spiral structures. Thus, in such cases, you should select “Elliptical Galaxy.” Select “Neither” if you identify your galaxy as an irregular.
 GALAXY CRUISE and Hubble Classification  (May 1, 2020, GALAXY CRUISE NEWS)

5.6 I want to perform the classification while comparing galaxies to the training images.

On the welcome page, click the GALAXY CRUISE logo at the left edge of the menu bar (see the figure below) to open the home page in another tab. If you click the “Training” item in the menu bar on the home page, you can perform the classification while consulting the training images.

5.7 I see something like an infinity symbol (∞) spin just after I classify a galaxy. What is that?

That symbol indicates that your classification is being sent. Don’t worry about it and keep going.


5.8 My evaluation criteria seem to have changed over the course of the classification exercises.

Perhaps, you have gotten used to the tasks. As you gain experience progressing through the stages and the number of galaxies you have classified increases, your criteria will inevitably change. Don't worry about the change. Please proceed to the subsequent stages.

5.9 Can I check whether my classifications are correct?

No, you can’t. Even researchers cannot definitively classify galaxies. If you are worried whether or not your classifications are correct, we recommend repeating the classifications in “Boötes Island” where you can compare your results with those of the Captain, until you gain confidence.
Practice in Boötes Island
There are some NEWS articles that will help you classify galaxies, so please refer to the articles provided below as needed. Results from different people for each galaxy are processed statistically when the Captain analyzes classification data, and as shown in the Captain’s reports in Season 1, Citizen Astronomers’ classifications have proven to be accurate. Please don’t worry too much over every single galaxy; trust in yourself and continue with your classifications.
Related NEWS Articles
 What are the distinguishing features of “fans”?  (March 1, 2020, GALAXY CRUISE NEWS)
 GALAXY CRUISE and Hubble Classification  (May 1, 2020, GALAXY CRUISE NEWS)
 Various Types of Galaxy Interactions and Mergers  (January 1, 2021, GALAXY CRUISE NEWS)
 Do you still get confused while classifying galaxies?  (February 1, 2021, GALAXY CRUISE NEWS)
 The Origins of Ring Galaxies  (January 1, 2022, GALAXY CRUISE NEWS)
 What is an Anemic Spiral Galaxy?  (February 1, 2022, GALAXY CRUISE NEWS)

5.10 How were the galaxies to be classified selected?

We selected galaxies with distances measured spectroscopically for ease of scientific analysis. This is very important because images captured by the Subaru Telescope contain numerous galaxies both near and far. Knowing their distances from us allows us to measure and analyze some of their physical properties such as true brightness, which would be difficult to determine without an accurate distance measurement.

6.1 What does it mean for two galaxies to collide?

When two galaxies happen to be close enough, they are attracted to each other through their mutual gravitational force. As the galaxy pair gets closer, the gravitational force between them becomes stronger and disturbs their morphologies. This process through which neighboring galaxies distort each other is called “gravitational interaction.” On some occasions, these galaxies can “collide” and even merge to form a larger galaxy. Because galaxies consist mostly of empty space with scattered stars and nebulae, when galaxies "collide" they actually pass through each other for the most part. But the violent gravitational interactions caused by passing through each other severely disrupt the shapes of the galaxies. 

6.2 Are there occasions when two different features coexist?

Yes. Particularly, “tails” (tidal streams) and “distortion” (distorted halos) are likely to occur in the same galaxy, and telling the difference between the two is often difficult. Depending on the viewing angle, “tails” and “fans” are sometimes difficult to distinguish as well. Such distinctions are difficult even for professional astronomers.
*If you are unsure which one to select, select the multiple answers that you think are likely.

6.3 Can one feature of colliding galaxies be mistaken for a different feature depending on the viewing angle?

Although such cases are thought to be rare, it is possible. For example, a “ring” seen from any direction cannot be mistaken for a “fan.” However, seen from the side view a “fan” may resemble a straight “tail” (tidal stream).

6.4 Are there any features other than these four (ring, fan, tail, and distortion)?

You may encounter some features that cannot be neatly classified into the basic four categories. Multiple features can coexist, and in exceedingly violent collisions, their shapes could be smashed into unrecognizable pieces. When galaxies are in the midst of a collision, their particularly bright cores (galactic nuclei) are sometimes arranged side by side (see the image below), creating yet another different feature.
* In this galaxy, you can also see "tails" (possibly "fans") and "distortion".



6.5 Why do interacting galaxies have various features?

The various features come from various forms of interaction. Some interactions involve a larger galaxy and a smaller one and other interactions involve galaxies with similar sizes. Some galaxy pairs interact head-on and others interact obliquely or just pass close to each other. You may also see galaxies just before or after interaction and some galaxies have experienced more interactions than others. In other words, the various features of interacting galaxies reflect the details of the interactions.
 The Origins of Ring Galaxies  (January 1, 2022, GALAXY CRUISE NEWS)

6.6 HIs there any case where features of interacting galaxies arise from causes other than galactic interactions?

Yes. Although the hypothesis that “rings” originate from galactic interactions is widely accepted, another hypothesis assumes that rings originate spontaneously. Although GALAXY CRUISE uses the former hypothesis and considers rings as interacting features, we also plan to test whether this assumption is true. Even if you suspect that some structures have origins not related to galactic interactions, please select the closest interacting feature displayed on the classification screen.
 The Origins of Ring Galaxies  (January 1, 2022, GALAXY CRUISE NEWS)

6.7 How can galaxies interact while the Universe is expanding?

Although in the grand scale the Universe as a whole is expanding, on the scale of galaxies, it is possible for gravity to overcome the expansion in the local area and pull galaxies together. In fact, the typical separation between galaxies is only a little larger than the typical size of a galaxy. For example, our Milky Way is headed toward the Andromeda Galaxy and predicted to merge with it in about four billion years. If we scaled the Milky Way’s disk, measuring 100,000 light-years in diameter, down to 10 centimeters, the Andromeda Galaxy would be located only about two meters away. It wouldn’t be difficult to roll a disk to hit a target two meters away. As you can see, the distances between neighboring galaxies are only a couple dozen times greater than their diameters, and the closer the pairs of galaxies get, the more strongly they attract one another. Therefore, galaxies actually interact quite frequently.

7.1 What should I do when I find an interesting object?

Please use the contact form to send us its coordinates and a brief description. To do so, move the object to the center of your display and save its image. If you click the “Screenshot” (camera-shaped) icon on the welcome page, the image will be saved and automatically downloaded. The coordinates of the object are shown at the bottom left of the screen as a pair of green numbers. In the case of the image below, for example, you should write “α=02:30:08.2909, δ=-04:32:04.5867” or “alpha=02:30:08.2909, beta=-04:32:04.5867” in the contact form.
You can also upload the downloaded image file on your Twitter or Instagram account with the #GALAXY_CRUISE hashtag instead of contacting us. In this case, please write "Credit: HSC-SSP/NAOJ" in addition to the coordinate.

* Currently, Screenshot is available only on Firefox, Google Chrome (greyscale only), and Safari. Clicking the camera icon on any of these browsers starts the download immediately, and then a dialog box for saving the file will appear, or the image will be automatically saved in a default location. As of April 2022, Screenshot does not work on Microsoft Internet Explorer or Microsoft Edge. On Google Chrome, color images cannot be downloaded as they exceed the browser’s file size limit. On Firefox, color images can be downloaded without any issues even for large file sizes, so you are encouraged to use Firefox (or Safari) until this problem is solved. 

7.2 Can I name the galaxies I’ve classified?

Unfortunately, you can’t. Every newly discovered celestial object should be assigned a unique designation because of scientific necessity. But if you find strange-shaped galaxies or other interesting objects, please give them nicknames and share them on Instagram. Perhaps some of your nicknames will go viral. 
 GALAXY CRUISE Official Instagram

7.3 Is it possible that an image may contain something other than celestial objects?

Yes. Since the displayed images (observation data) are unprocessed, you may find camera artifacts or false features in them. You may also find fast-moving celestial objects, such as asteroids, traveling across the sky. In the image shown in question 6.1, for example, the spike-like line running horizontally at the bottom right is an artificial feature.
Strange Features in Images (from Exploring the Universe with Subaru Telescope Data”)

7.4 Can I use the image materials without permission?

You can use our image materials without prior permission within the following scope: 
- Extent of free use stipulated by Japanese copyright law (private use, educational use, news reporting, etc.)
- Usage in academic research, education, and learning activities
- Usage by news organizations
- Usage in printed media
- Usage in websites and social networks
When using the materials, you should include the following credit line: “Credit: NAOJ.” For more information, see the Guide to Using NAOJ Website Copyrighted Materials.

8.1 What is Citizen Astronomy (Citizen Science in Astronomy)?

Please see About Citizen Science.

8.2 Why are you conducting this project?

Please see A Word from the Captain.

8.3 Is this the first attempt (in the world) to classify interacting galaxies?

It’s not the first. There actually are many examples where researchers have classified galaxies in telescope images, and some were even conducted as citizen science projects. Compared with the images captured by other instruments, however, those captured by HSC are overwhelmingly superior in the extent of the survey area and the "depth" (quality) of data which determines how well you can recognize dim and faint objects. Since the telltale signs of galaxy collisions are often faint, we expect HSC images will allow a detailed analysis that cannot be performed with other images. In Season 1, many spiral structures and interacting features that were not found in previous studies were revealed by Citizen Astronomers.

8.4 How will the classified results be used?

Researchers will statistically analyze the data obtained for galaxies classified by multiple participants. When the analysis of the various galaxies moves ahead and is written up as a research paper, we would like to acknowledge the contribution of all the Citizen Astronomers, as a group, who helped with the classification.
 The Latest Scientific Analysis by the Captain  (March 1, 2021, GALAXY CRUISE NEWS)
 Season 1 Report by the Captain  (September 27, 2021, YouTube video)

8.5 Isn’t it better to apply machine learning than to have non-specialists classify galaxies?

Actually, attempts to search for interacting galaxies with machine learning are beginning, but so far classification with human eyes is still essential. Before using machine learning, we first have to create classification samples, or “teaching data,” of interacting galaxies. However, there are still no such data available for the classification of faint galaxies imaged with HSC or other instruments. To create the data, we first need to systematically analyze classification results provided by many people. In addition, by many people participating in the classification, we can share the pleasures of participating in real astronomy and determining the growth history of galaxies. More than machines, humans can better appreciate the stunning images captured by HSC!
 GALAXY CRUISE and Machine Learning  (September 1, 2020, GALAXY CRUISE NEWS)

Now, Let's Start on Your Adventure!