Popular galaxy full of standard candles features as Hubble Picture of the Week

Astronomers have long been interested in NGC 3370, a spiral galaxy located about 90 million light-years away in the constellation Leo (The Lion). They have observed the galaxy multiple times in the past.

A previous Hubble image of NGC 3370 was released in 2003. But this present observation offers more. It includes wavelengths of light that were not included in the previous image.

The image shows blue star clusters scattered around the galaxy’s spiral arms. The center of the galaxy, as seen in the image, beams with a yellowish-white light. Dark reddish dust threads swirl around the center. Two medium-sized and several small distant galaxies are seen in the background of the image.

While NGC 3370 has eye-catching features, what makes it a galaxy of high interest is the Cepheid stars and type Ia supernovae that have been observed in it. These objects are important because astronomers use them to determine how far away a galaxy is.

Cepheid stars are variable stars that pulsate radially. These stars change in both brightness and size. By measuring the pulsation period, astronomers can calculate how luminous a Cepheid star is. Comparing that brightness with how faint the star looks from Earth gives its distance.

Type Ia supernovae, on the other hand, are the final explosive death of a white dwarf star in a binary system. Their measured brightness tells how far away it is. Since Hubble’s law implies that the farther away a galaxy is from Earth, the faster it is moving away, astronomers can calculate how fast the Universe is expanding.

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