Hubble photographs a Virgo spiral whose core rotates at right angles to its disk

Gas arriving from outside a galaxy does not have to arrive in the plane of the disk. Tilted gas can settle into its own plane and form stars there, leaving a center whose rotation axis is not the outer disk's. The Hubble text puts that forward conditionally: if NGC 4698 funneled in gas from an outside source, the newly collected gas could have formed a disk of gas and stars in the galaxy's center, at an angle relative to the rest of the disk ^[10]. The other explanation offered is a minor merger in the galaxy's past, suggested by a short tail of hydrogen streaming from one side ^[11].

Both are offered as possibilities. One is a conditional, the other a suggestion carried by a single morphological feature, and separating them would take velocity measurements of that hydrogen.

The new picture documents shape. The bulge glow appears above and below the dusty disk, which is the elongation seen in this projection ^[7]. Rotation, though, is a velocity, and an exposure records positions and brightness ^[8], so the kinematic claim rests on other data. The releases do not say how many spirals with right-angle bulges are known ^[20].

The bulge's off-white glow comes from stars smaller, older and cooler than the blue stars dotting the outer disk ^[4]. Those stars orbit a supermassive black hole of millions of solar masses, and the release reports signs that it is actively growing as its gravity draws gas inward ^[5].

The Virgo Cluster enters through the programme's goals. Researchers will use the data to learn how a galaxy's journey through a cluster affects its evolution and its ability to form new stars ^[14]. For NGC 4698 itself, the named cause is an outside source of gas or a minor merger, and the cluster appears in these releases as the survey's subject ^[21]. In my view the galaxy is a candidate case for the cluster question, and the answer will come from the rest of the sample.

One note on the record. The phys.org, NASA and ESA postings carry the same text, opening on the same sentence about a galaxy that "seems serene" but "hides a chaotic secret" ^[17], and NASA credits the words to ESA/Hubble ^[15]. The three postings are one account published three times ^[16]. Only the ESA version identifies the programme as 18103, with Thilker as principal investigator ^[12][19]. At about 55 million light-years, the light in this frame left NGC 4698 roughly 55 million years ago ^[1][18].