With the expansion of the universe, which galaxies are approaching the earth?

M90 galaxy photographed by Hubble Space Telescope. The galaxy is about 60 million light years away from the Milky Way, but unlike most galaxies, it is getting closer and closer to us.

Recent images taken by Hubble Space Telescope depict M90 galaxy, a spiral galaxy in Virgo, about 60 million light years away from the Milky Way. Unlike most galaxies, this galaxy is getting closer and closer to us.

The photo itself is incredible, but what is even more fascinating is the information that astronomers found when they took this photo. M90 galaxy is one of the few galaxies moving towards the Milky Way. By observing the light emitted by M90, scientists concluded that the galaxy is getting closer and closer to us.

When this galaxy approaches us, it will compress the wavelength of its light, which is like a toy spring. When you squeeze one end, it will be squashed. In the visible spectrum, shorter wavelengths appear blue. Therefore, the light of M90 galaxy is compressed, showing a phenomenon called "blue shift", which indicates that M90 is approaching us.

The statement of the Hubble telescope team pointed out that almost all the galaxies we can observe are moving away from us with the expansion of the universe. We see that the light of these galaxies extends to the red end of the visible spectrum, which is called red shift.

M90 galaxy is a part of Virgo galaxy cluster, which consists of more than 1200 galaxies. Astronomers say that the blue shift of M90 galaxy probably stems from the amazing mass of the Virgo galaxy cluster. Under its action, the galaxies in the cluster will accelerate and be sent into strange orbits. Over time, these strange orbits will make galaxies sometimes close to the earth and sometimes far away from it.

The Virgo cluster itself is moving away from us, but some galaxies in the cluster, including M90, are moving faster than the whole cluster. Therefore, from the earth's point of view, these galaxies are moving towards us, even though other galaxies in the same cluster seem to be moving away from us at high speed.

This Hubble Space Telescope M90 galaxy image combines infrared, ultraviolet and visible light. Because the camera that took this photo consists of four photodetectors with overlapping fields of view, one of them has a higher magnification than the other three, so there is a staircase-like black area in the upper left corner of this photo.

Messier objects M75 (globular cluster) is located in Sagittarius, about 67,500 light years away from the Earth.

Knowledge points:

messier objects

The M90 galaxy was discovered by French astronomer Charles Messier in 178 1 year. Messier's most famous achievement is to make an astronomical table of deep space objects, numbering nebulae, clusters and galaxies. This is the famous messier Cluster Nebula Table.

Messier himself is only interested in finding comets, but he has been looking for fixed celestial bodies that are easily mistaken for comets, but he can't find real comets. Frustrated by this, he and his assistant Pierre Shangmei created a list of non-comet objects to distinguish fixed objects that are easily confused with comets. This is a list of later messier cluster nebulae. This is one of the most commonly used and important celestial tables in astronomy, and it is also the first detailed and accurate catalogue of celestial bodies. The celestial bodies on the list have always been called "messier objects" by professional and amateur astronomers, and their codes (from M 1 to M10) are still widely used in astronomy, including the Andromeda galaxy represented by M3 1.

The list of messier cluster nebulae contains almost five of the most spectacular deep-space objects that can be observed in Europe, namely diffuse nebulae, planetary nebulae, open clusters, globular clusters and galaxies. They are the brightest and most attractive deep space objects, and they are also the research and shooting targets of amateur astronomers today.

Blue shift and red shift

In physics, redshift refers to the phenomenon that the wavelength of electromagnetic radiation increases and the frequency decreases for some reason. In the visible band, the spectral lines of the spectrum move to the red end for a certain distance. Conversely, if the wavelength of electromagnetic radiation becomes shorter and the frequency becomes higher, it is called blue shift. Scientists have observed the phenomenon of redshift in the spectra of distant galaxies, quasars and intergalactic gas clouds, which is called "cosmic redshift", and its increase ratio is proportional to the distance, which provides strong support for the viewpoint of universe expansion (such as the Big Bang universe model).

Another form of redshift is gravitational redshift, which is a relativistic effect observed when electromagnetic radiation propagates away from gravitational field. On the other hand, when electromagnetic radiation propagates near the gravitational field, the gravitational blue shift will be observed, and its wavelength will become shorter and its frequency will increase.

Astronomers have also observed many blue shifts, such as the Andromeda galaxy, which is moving towards the Milky Way. From the perspective of the earth, the light emitted by this galaxy has a blue shift. When observing spiral galaxies, the end of their spiral arms near the earth will appear blue shift.