As their name suggests, elliptical galaxies are round or oval, with stars distributed fairly uniformly throughout. They have a bulge and halo, like spiral galaxies, but don’t have the flat disk of stars. The stars in ellipticals tend to be older.
Irregular galaxies
What do all galaxies have in common?
Galaxies have certain features in common.
Gravity holds the billions of stars together
, and the densest region is in the center, called a core or bulge. Some galaxies have spiral or pinwheel arms. All galaxies have a faint outer region or envelope and a mysterious dark matter halo.
How are spiral and elliptical galaxies similar?
Spiral galaxies have a central bulge of stars surrounded by a disk that contains arms, which form a spiral structure. …
Elliptical
galaxies don’t show any structure, but have a smooth ellipsoidal shape, appearing as a large spherical or elliptical ball of stars.
What do all irregular galaxies have in common?
Irregular galaxies have no particular shape. They are among the smallest galaxies and are
full of gas and dust
. Having a lot of gas and dust means that these galaxies have a lot of star formation going on within them.
What do spiral galaxies have in common?
Most spiral galaxies contain
a central bulge surrounded by a flat, rotating disk of stars
. The bulge in the center is made up of older, dimmer stars, and is thought to contain a supermassive black hole. Approximately two-thirds of spiral galaxies also contain a bar structure through their center, as does the Milky Way.
What are 3 characteristics of elliptical galaxies?
There are four distinguishing characteristics of the ellipticals: (a)
they have much more random star motion than orderly rotational motion
(star orbits are aligned in a wide range of angles and have a wide range of eccentricities); (b) they have very little dust and gas left between the stars; (c) this means that they …
Why does elliptical galaxy look like one giant star?
An elliptical galaxy looks as if it is a giant star
because it lacks the distinctive structure of a spiral galaxy, where the bulge is surrounded by a
…
What is the big BNAG theory?
At its simplest, it says the universe as we know it started with an infinitely hot, infinitely dense singularity, then inflated — first at unimaginable speed, and then at a more measurable rate — over the next
13.8 billion years
to the cosmos that we know today.
What is the force that holds galaxies together?
Most galaxies are not alone in the vast expanse of space, but are connected to one or more other galaxies by
gravity
. The same force that holds you onto the Earth can keep many individual galaxies bound together.
What galaxy do we live in?
We live in one of the arms of a large spiral galaxy called
the Milky Way
. The Sun and its planets (including Earth) lie in this quiet part of the galaxy, about half way out from the centre. 100 000 years to cross from one side to the other.
How do we know we live in a spiral galaxy?
1)
When you look toward the Galactic Center with your eye
, you see a long, thin strip. This suggests a disk seen edge-on, rather than a ellipsoid or another shape. We can also detect the bulge at the center. Since we see spiral galaxies which are disks with central bulges, this is a bit of a tipoff.
How do stars move in an irregular galaxy?
The stars then move on elliptical orbits around the center, but are perturbed by
local irregularities
. In spirals and elliptical, the potential is rather symmetric, whereas in irregulars it is quite… irregular.
What holds an irregular galaxy together?
The centrifugal force of the spinning gas cloud along with the gravitational pull within the clouds
work together to give a galaxy its shape. All galaxies began with an elliptical shape, which is mostly a result of the centrifugal force of the spinning gas cloud.
Why is the galaxy spiral?
Astronomers believe that galaxies have spiral arms
because galaxies rotate – or spin around a central axis
– and because of something called “density waves.” Galactic density waves are like water waves. … A spiral galaxy’s rotation, or spin, bends the waves into spirals.
How old is a spiral galaxy?
It was formed
around 12.4 billion years ago
. Astronomers have identified the oldest known spiral galaxy in the universe, which was formed around 12.4 billion years ago, after rediscovering a fuzzy, forgotten photo taken by the Atacama Large Millimeter/submillimeter Array (ALMA).
Where are the oldest stars in a spiral galaxy?
The Milky Way’s bulge
— a bulbous, 10,000 light-year-wide region of stars and dust popping out of the galaxy’s spiral disc — is thought to contain some of the oldest stars in the galaxy.
