A wide range of astronomical software is available for Ubuntu.
Official packages
Ubuntu includes many packages useful for astronomy and astrophysics.
Stellarium
Stellarium is a free open source planetarium for your computer. It shows a realistic sky in 3D, just like what you see with the naked eye, binoculars or a telescope. Developed at ESO, and used as a base in VirGO, a VO tool for European astronomers.
Celestia
A real-time visual space simulation
Choose a point within the Local Group of galaxies, and Celestia will show you an approximation of how it would appear to your eyes were you actually there. Orbit a couple kilometers above the surface of a tiny, irregular asteroid, then head off towards Jupiter, watching it grow from a bright point of light into a looming sphere filling your field of vision.
Leave our solar system entirely and observe the sun as it fades from a brilliant disk to a bright star, disappearing almost entirely as you head off toward the Upsilon Andromeda system to orbit around its innermost giant planet.
Celestia is available with a range of front-ends
Fv
A tool for viewing and editing FITS-format files
Fv provides a graphical user interface to data stored in FITS (Flexible Image Transport System) files. Local files can be created, viewed and edited, files on the internet can be opened read-only through the http and ftp protocols. Through the POWplot program, FITS data can be visualized in a large variety of styles. An interface to the Sky-View online database allows for searching, downloading, and plotting of images and object lists for a region of the sky.
FITS support is also available through The GIMP
GCX
Astronomical image processing and photometry
Gcx is an astronomical image processing and data reduction tool, with an easy to use graphical user interface. It provides a complete set of data reduction functions for CCD photometry, with frame WCS fitting, automatic star identification, aperture photometry of target and standard stars, single-frame ensemble photometry solution finding, multi-frame color coefficient fitting, extinction coefficient fitting, and all-sky photometry; as well as general-purpose astronomical image processing functions (bias, dark, flat, frame alignment and stacking); It can function as a FITS viewer.
The program can control CCD cameras and telescopes, and implement automatic observation scripting. Cameras are controlled through a hardware-specific server, to which gcx connects through a TCP socket. It generates FITS files with comprehensive header information.
IFRIT
A powerful tool for visualizing 3-dimensional data sets
IFRIT (the Ionization FRont Interactive Tool) has its origins (and hence name) in a specialized utility designed to visualize ionization fronts in cosmological numerical simulations. IFRIT, however, has outgrown its origins and now can visualize general data sets as well.
KStars
A desktop planetarium application
KStars is a graphical desktop planetarium for KDE. It depicts an accurate simulation of the night sky, including stars, constellations, star clusters, nebulae, galaxies, all planets, the Sun, the Moon, comets and asteroids. You can see the sky as it appears from any location on Earth, on any date.
The user interface is highly intuitive and flexible. The display can be panned and zoomed with the mouse, and you can easily identify objects and track their motion across the sky. KStars includes many powerful features, yet the interface is clean and simple and fun to use.
Unofficial astronomy packages
None listed
Other astronomy software not in Ubuntu
CASA - "Common Astronomy Software Applications package, is being developed with the primary goal of supporting the data post-processing needs of the next generation of radio astronomical telescopes such as ALMA and VLA."
Starlink - Collection of advanced analysis tools for astronomical research
Galaxy - Simple galaxy-formation simulation
XEphem - Advanced ephemeris software
Nightfall - Eclipsing binary star simulator, which can produce animations
AVSOMAT - Variable-star observation automation software
Starmap - Displays a (3D) map of stars in our region of the Galaxy
Open Source Astronomy - Massive collection of open-source astronomical software
ImageJ - Advanced image-processing software
Nova - Integrated observational environment for amateur astronomers
MIRIAD - Multichannel Image Reconstruction, Image Analysis and Display, MIRIAD an radio interferometry data reduction package.
IRAM GILDAS - GILDAS is a (sub-)millimeter radio interferometry data reduction and analysis software.
Karma Toolkit - Karma is a toolkit for interprocess communications, authentication, encryption, graphics display, user interface and manipulating of astronomical data.
VirGO - Visual Browser for the ESO Science Archive Facility (Virtual Observatory built in to Stellarium).